Hm, ok, I don't use CDs (in any wax), but I think you are correct that the 20 is too big for that jar.
There are a few things to keep in mind when working with palm wax:
- it has a high melt point, so it needs a lot of heat to get it going
- once it melts, it is very viscous, so it needs a wick that can "draw up" a lot of wax
- it is an acidic wax, so it needs a wick that can withstand an acidic environment
Thats why CSNs are so successful, they make big hot flames, they draw up a lot of wax, and they have a special treatment to withstand acidic wax. Some RRDs have the NST treatment for palm wax, so they also do well.
Once we start using wicks meant for soy or parrafin, the common problems that arise are that the wicks don't burn hot enough, don't draw up enough wax, and may combust incompletely from the acidic wax. To overcome those problems, we use wicks that are much larger than what would be appropriate for soy or parrafin. Now the flame is hot enough to melt the palm wax, but the wick is so huge, it's drawing the wax too quickly and burning it off at much quicker rate. Also, because of the super fast combustion, the fragrance oil may be "burned off" instead of wafting through the air, making for poor throw. All that isn't to say that it's impossible to make a good palm candle with a series like LX, CD, HTP or the Premiers. It's definitely possible, you are just going to have to get really good a learning the signs of a good burn versus an adequate burn or poor burn.
Definitely give your palm candles a good two week cure. I know it's hard to wait, but they'd really do need that cure time for you to judge if the wick is throwing well or not.
It sounds like you are on the right track with leaving a shell that melts down. Palm is so different from other waxes.
I don't know if it will help, but I am going to attach some pics of my candles in various states of burn. 😁
This candle is is just a smidge under wicked, I used a CSN 9 and I think it would do better with a 12. I'm down to that last quarter of the jar, and while the sides are weeping down nicely, when you see the overhead view next some issues will be apparent.
This is the overhead view, and hopefully you can see there are multiple perimeters to the melt pool. That is to be expected when we are looking at the first half or so of a jar this size (that's a 3" jar), but this far down I want the melt pool to even itself out. The HT is only so-so, and I think in part it's the wick, but I also have a feeling this just not a powerhouse FO.
This is a multi-wick loaf style jar, with three Premier 745 wicks. They've been lit for about an hour here. This jar is 3" wide and about 8" long. The three 745s are not doing a good job here. The flames are small, and for it being the bottom of the container, the MPs are small. I know the sides look good, but just last night I peeled giant sheet of wax off the sides to put in my melter. 😂 I confess, I mess with my candles! Next time I pour this, I'll use 755s. I like Premiers for multi-wick jobs. If I were to try to wick this in CSNs, the smallest I could use would be a CSN 7, and even with just two wicks that would probably be over wicked. So case in point when an alternative wick series may be better. This candle is throwing great, btw. Christmas Splendor from NG, 6%, immediate strong HT from the first burn after a 9 day cure.
This candle above is absolute perfection. I have been burning it since the beginning of November. Generally three to four hour burns, once a week... how many hours is that? A lot, lol. You can see the sides have melted down beautifully. It had a shell up until maybe two burn ago, when the jar finally got hot enough to start pulling it down. The wax has been at the exact same level for several burns now, as the wick consumes the shell. The HT is phenomenal. That's a 16oz salsa jar with a CSN 14.
This is the top vie, and you can see it has just a bit of a ledge, but otherwise the MP is quite even. Honestly, this is probably due to a slightly off center wick and the slight curl to the wick. Don't mind the red, that's me playing with my candles again. 😆 I dipped the red candle's wicks, then used the same dipper on the green candle. This FO is Alpine Cheer from Flaming, at 6%. I love, love, love it, and it is throwing like crazy.
Sorry, I thought I had a couple pics of candles in the early stages of their burn, but I guess not. I really try not to pass final judgement on a wick until the very end of the burn. With palm wax, so much happens at the bottom of the jar. The kiss of death in the early stages would be an obvious problem like a teeny tiny flame or a tiki torch. Anything other than that, I'm going to let it burn and see what happens. Sometimes poor HT early on that develops into good HT further down is an indication that's the wick is close but need tweaking. Poor HT the whole time, accompanied by a good flame and burn behavior could mean it's the FO.
Ok, sorry about the massive wall of text and photos, hopefully you can glean some good stuff out of all that. 😅
If if you can, get some pics of the candles you've been working on so we can see what's up.